Household refrigeration appliance having a closed loop speed-controlled fan and method for operating a household refrigeration appliance having a closed-loop speed-controlled fan

ABSTRACT

A household refrigeration appliance has a thermally-insulated body with an interior container that delimits a coolable interior space, a refrigeration circuit for cooling the coolable interior space and at least one fan. During the proper operation of the household refrigeration appliance, the fan is operated in a closed loop speed-controlled manner according to an at least indirectly specified desired rotational speed of the fan. During an inspection mode, the fan is operated without closed loop speed control, the actual rotational speed of the fan is ascertained and the actual rotational speed is evaluated in order to detect an abnormal operating state of the fan.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority, under 35 U.S.C. § 119, of Germanpatent application DE 10 2018 212 127.3, filed Jul. 20, 2018; the priorapplication is herewith incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a household refrigeration appliance having aclosed loop speed-controlled fan and a method for operating a householdrefrigeration appliance having a closed loop speed-controlled fan.

Household refrigeration appliances comprise a thermally-insulated bodyhaving an interior container that delimits a coolable interior space forstoring foodstuffs, and a refrigeration circuit for cooling the coolableinterior space. Household refrigeration appliances may also include aclosed loop speed-controlled fan. The fan may be subject to abnormaloperation.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a householdrefrigeration appliance with a closed-loop speed-controlled fan and amethod of operating such a household refrigeration appliance, whichovercome the a variety of disadvantages associated with theheretofore-known devices and which provide for a possibility to detectan abnormal operating state of the closed loop speed-controlled fan.

With the foregoing and other objects in view there is provided, inaccordance with the invention, a method of operating a householdrefrigeration appliance that comprises a thermally-insulated body withan interior container that delimits an interior space, a refrigerationcircuit for cooling the interior space, and at least one fan, The methodcomprises the following method steps:

during a regular operation of the household refrigeration appliance,operating the fan under closed loop speed control according to aspecified desired rotational speed of the fan; and during an inspectionmode, operating the fan in without closed loop speed control,ascertaining an actual rotational speed of the fan and evaluating theactual rotational speed with an electronic control unit of the householdrefrigeration appliance in order to detect an abnormal operating stateof the fan.

In other words, the objects of the invention are achieved by a methodfor operating a household refrigeration appliance that comprises athermally-insulated body having an interior container that delimits acoolable interior space that is provided for storing foodstuffs, arefrigeration circuit for cooling the coolable interior space and atleast one fan, the method including, during the proper operation of thehousehold refrigeration appliance, operating the fan in a closed loopspeed-controlled manner according to an at least indirectly specifieddesired rotational speed of the fan, and during an inspection mode,operating the fan in a manner without closed loop speed control,ascertaining the actual rotational speed of the fan and evaluating theactual rotational speed in particular by means of an electronic controlunit of the household refrigeration appliance in order to detect anabnormal operating state of the fan.

The object of the invention is also achieved by way of a householdrefrigeration appliance that comprises a thermally-insulated body withan interior container that delimits a coolable interior space that isprovided for storing foodstuffs, a refrigeration circuit for cooling thecoolable interior space and at least one fan, wherein the householdrefrigeration appliance is configured so as to perform the methodaccording to the invention. The household refrigeration applianceaccording to the invention is consequently in particular configured soas, during the proper operation of said household refrigerationappliance, to operate the fan in a closed loop speed-controlled mannercontrolled by means of the electronic control unit, and during aninspection mode to operate the fan in a manner without closed loop speedcontrol, to ascertain the actual rotational speed of the fan, forexample by means of a tachometer or signals from its tachometer, and bymeans of the electronic control unit to evaluate the actual rotationalspeed in order to detect an abnormal operating state of the fan.

The household refrigeration appliance comprises the thermally-insulatedbody having the interior container that delimits the coolable interiorspace that is provided for storing foodstuffs, and the refrigerationcircuit. The refrigeration circuit is preferably configured in such amanner that it cools the coolable interior space at least approximatelyto a specified temperature.

Refrigeration circuits as such are known in principle to the personskilled in the art and comprise in particular an evaporator that isprovided to cool the air for the coolable interior space, a compressorand a condenser.

The household refrigeration appliance according to the invention may befor example a household refrigerator. In this case, the coolableinterior space is cooled to temperatures greater than 0° C. Thehousehold refrigeration appliance according to the invention may howeveralso be a household freezer or a fridge-freezer combination. Thehousehold refrigeration appliance according to the invention maycomprise precisely one coolable interior space but may also comprisemultiple coolable interior spaces.

The household refrigeration appliance according to the invention mayalso be configured as a wine refrigerator that is provided to storebottles that are filled with a drinkable fluid, in particular wine.

The household refrigeration appliance may comprise a duct system thatruns for example within the thermally-insulated body and is connected inparticular via an opening to the coolable interior space. The evaporatorand the fan are arranged in the duct system with the result that the fantends to convey air that is cooled by the evaporator into the coolableinterior space.

The fan comprises in particular an electric motor and a rotatablymounted fan wheel that may be set into rotation by means of the motor.

The speed of the fan is controlled in a closed loop manner, in otherwords the household refrigeration appliance comprises a feedback controlfor the closed loop speed control of the fan with the result that thefan or rather its fan wheel rotates in a closed loop speed-controlledmanner during the proper operation at a specified rotational speed.

During the proper operation of the household refrigeration appliance, itis possible for the evaporator to ice up, in that in particular ice isformed on its surface. In order in particular to remove the ice, it ispossible to provide for de-icing the evaporator in particular in amanner controlled by means of the electronic control unit, in that saidevaporator is warmed for example by means of a heating device that maybe controlled by the electronic control unit. In accordance with oneembodiment of the method according to the invention or rather of thehousehold refrigeration appliance according to the invention, theabnormal operating state of the fan is an icing-up of the evaporatorthat is arranged in the duct system.

The household refrigeration appliance is in particular configured so asin the inspection mode to detect the abnormal operating state of thefan, in particular a potential icing-up of the evaporator, by means ofevaluating the actual rotational speed of the fan. In order to ascertainthe actual rotational speed, the fan comprises for example a tachometerthat is connected to the electronic control unit.

The abnormal operating state of the fan may also be a failure of thefan.

The fan may be provided so as to convey air that is warmed by thecondenser into the environment of the household refrigeration appliance.It is then possible to provide that, on the basis of the detectedfailure of this fan, the compressor is operated in a gentle operatingmode controlled by means of the electronic control unit. The compressoris for example a closed loop speed-controlled compressor. A gentleoperating mode is for example an operation of the compressor at a lowerrotational speed.

The condenser may become contaminated during operation. A contaminatedcondenser may be an abnormal operating state of the fan that is arrangedin the condenser. In particular, if the condenser is configured as aroll or lamella condenser, this may impair the operation of the fan thatis arranged in the condenser and this may be detected by means ofevaluating the actual rotational speed of the fan during the inspectionmode. In the event that it is detected that the condenser iscontaminated, it is then possible to provide for operating the condenserin a gentle operating mode controlled by means of the electronic controlunit.

It is also possible by means of evaluating the actual rotational speedof the fan to detect a function of the fan during the inspection mode.

The fan may experience a change in its load as a result of external orinternal influences which may have an effect on its rotational speedwhen operating in a manner without closed loop speed control (inspectionmode). For example, a malfunction of the fan or preferably an icing-upof the evaporator is detected by way of example by virtue of a change inthe detected rotational speed. It is also possible to detect the statusof the fan itself in order for example to energetically optimize thedevice behavior with the aid of this information. Consequently, it ispossible using a rotational speed measurement of the fan to conclude thestate of the fan while the household refrigeration appliance is in theinspection mode. It is thus possible to detect a change in the state ofthe household refrigeration appliance, for example an icing-up of theevaporator or damage to the fan. The fan may as a consequence beconsidered in particular in parallel to its fan function as a sensingunit.

An icing-up of the evaporator causes in particular a change in the flowbehavior of the duct system and thus a change in the load of the fan. Ifthe fan is operated in a closed loop speed-controlled manner, then it isoperated at the desired rotational speed essentially independently ofthe load of the fan. According to the invention, the fan is thereforeoperated in a manner without closed loop speed control in the inspectionmode, in other words the closed loop speed control of the fan isdeactivated during the inspection mode.

Consequently, when the fan is operated in a manner without closed loopspeed control in the inspection mode, a change in the load of the fanfor example as a result of the evaporator icing-up influences its actualrotational speed, as a result of which it is possible by means ofevaluating the actual rotational speed during the inspection mode toconclude in particular that the evaporator has iced up.

The household refrigeration appliance may preferably comprise aninverter that has pulse-width modulation and is provided so as tocontrol the fan. The inverter is operated in particular during theinspection mode with a predetermined duty cycle that is allocated to theinspection mode.

A feedback control that is required for the closed loop speed controlmay be realized for example by means of the electronic control unit thatthen for example directly controls the inverter.

The household refrigeration appliance may preferably comprise a closedloop controller that is controlled by the electronic control unit and isprovided so as to control the inverter and to operate the fan in aclosed loop speed-controlled manner. Consequently, it is possible forexample to combine the fan, the inverter and the closed loop controllerinto one assembly. The electronic control unit provides in this caseinformation for example to the closed loop controller as to whether thefan is to be operated in the closed loop speed-controlled operation orfor the inspection mode is to be operated in the operation withoutclosed loop speed control.

In the closed loop speed-controlled operation, it is also possible toprovide for the fan to be operated at different rotational speeds.

It may preferably be provided by means of the electronic control unitspecifying to the closed loop controller the predetermined duty cyclethat is allocated to the inspection mode to deactivate the closed loopspeed control of the fan that may be performed by the closed loopcontroller so that the fan is controlled by the inverter in a mannerwithout closed loop speed control during the inspection mode.Consequently, the closed loop controller that is configured for exampleas a microcontroller is configured in particular in such a manner thatit deactivates the closed loop controller for the predetermined dutycycle that is allocated to the inspection mode in order to operate thefan in an uncontrolled manner, in other words in a manner without closedloop speed control.

The inspection mode may prevail for example for a specified time period.

In accordance with an added feature of the invention, the fan may beoperated in a closed loop speed-controlled manner prior to and/or afterthe inspection mode.

It may also be provided that directly after starting up the fan fromstandstill said fan is initially operated in a manner without closedloop speed control for a predetermined time period in the inspectionmode and after the end of the predetermined time period is operated in aclosed loop speed-controlled manner. Where appropriate, it is alsopossible directly prior to the inspection mode to perform a start-upphase of the fan from standstill, this phase being performed in a mannerwithout closed loop speed control or in a closed loop speed-controlledmanner.

The actual rotational speed may be evaluated during the inspection modefor example by means of comparing the actual rotational speed with arotational speed of the fan that is to be expected for a normaloperating state of the fan, in particular for an evaporator that is noticed-up.

On the basis of the evaluated actual rotational speed of the fan duringthe inspection mode, it is possible to initiate a procedure of de-icingthe evaporator, in that for example the electronic control unit switcheson a heating device so as to de-ice the evaporator after the prevailingcooling phase.

It is possible owing to the iced-up evaporator that the load of the fanreduces. The procedure of de-icing the evaporator is then initiated forexample if the actual rotational speed exceeds a predetermined thresholdvalue during the inspection mode.

Based on the method according to the invention or rather on thehousehold refrigeration appliance according to the invention, it ispossible to detect the function and the state of the fan for example viaa tachometer signal despite an internal closed loop speed control of thefan.

This is achieved in particular by means of deactivating the closed loopspeed control function for example in the case of a predetermined dutycycle or for a specific time after the start-up of the fan, as a resultof which the load for a fan is detected despite the possibility of aclosed loop speed control function via the tachometer signal.

A change in the load of the fan may be a result of different causes.Examples of such causes are air with a high moisture content or anicing-up of the evaporator which result in a change in the cross sectionof the duct system.

By virtue of detecting the load on the fan, it is possible for exampleto improve the control of the household refrigeration appliance, (by wayof example: initiating a defrosting phase or rather initiating aprocedure of de-icing the evaporator).

Other features which are considered as characteristic for the inventionare set forth in the appended claims.

Although the invention is illustrated and described herein as embodiedin a household refrigeration appliance having a closed loopspeed-controlled fan and method for operating a household refrigerationappliance having a closed-loop speed-controlled fan, it is neverthelessnot intended to be limited to the details shown, since variousmodifications and structural changes may be made therein withoutdeparting from the spirit of the invention and within the scope andrange of equivalents of the claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a perspective view of a household refrigeration appliance;

FIG. 2 is a partial view of a duct system of the household refrigerationappliance;

FIG. 3 is a partly schematic view of a closed loop speed-controlled fanof the household refrigeration appliance;

FIG. 4 is a timing diagram that illustrates the operation of the fan;

FIG. 5 is a similar diagram that illustrates the operation of the fan;and

FIG. 6 is a schematic illustration of a compressor of a refrigerationcircuit of the household refrigeration appliance.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures of the drawing in detail and first,particularly, to FIG. 1 thereof, there is shown a perspective view of ahousehold refrigeration appliance 1 that comprises a thermally-insulatedbody 2, also referred to as a housing or a carcass, with an interiorcontainer 3 that delimits a coolable interior space 4. The coolableinterior space 4 is provided for storing foodstuffs.

The household refrigeration appliance 1 comprises in the case of thepresent exemplary embodiment a door leaf 10 that is mounted on the body2 in such a manner as to be able to pivot in particular with respect toa vertically extending axis. The coolable interior space 4 is accessiblewhen the door leaf 10 is in the open state and the coolable interiorspace 4 is closed when the door leaf 10 is in the closed state.

In the case of the present exemplary embodiment, multiple door trays 6for storing foodstuffs are arranged on the side of the door leaf 10 thatis facing the direction of the coolable interior space 4. In particularmultiple compartment trays 7 for storing foodstuffs are arranged in thecoolable interior space 4. A drawer 8 is arranged in the lower region ofthe coolable interior space 4. The drawer is likewise used for storingfood. One of the compartment trays 7 that covers the upwardly positionedopening of the drawer 8 is arranged above the drawer 8.

The household refrigeration appliance 1 comprises a refrigerationcircuit 5 that is known in principle to those of skill in the art, forcooling the coolable interior space 4. With reference to FIG. 2, therefrigeration circuit 5 comprises inter alia an evaporator 20.

The household refrigeration appliance 1 comprises in the case of thepresent exemplary embodiment an electronic control unit 9 that isconfigured so as to control the refrigeration circuit 5 such that thecoolable interior space 4 assumes at least approximately a specifieddesired temperature or a desired temperature that may be specified. Theelectronic control unit 9 is preferably configured in such a manner thatit controls the temperature of the coolable interior space 4 in aclosed-loop manner. In order where appropriate to obtain the actualtemperature of the coolable interior space 4, the householdrefrigeration appliance 1 may comprise at least one temperature sensor(not illustrated in detail) connected to the electronic control unit 9.

With reference to FIG. 2, the household refrigeration appliance 1comprises a duct system 21 that is arranged in particular within thethermally-insulated body 2 and is connected to the coolable interiorspace 4 via an opening 11. The evaporator 20 is arranged in the ductsystem 21.

A fan 22 is arranged in the duct system 21. The fan 22 is provided, inits activated state, to convey air that is cooled by the evaporator 20into the coolable interior space 4 via the duct system 21 and via theopening 11.

The fan 22 comprises an electric motor 23 and a fan wheel 24 that may berotated by means of the motor 23 (FIG. 3).

The household refrigeration appliance 1 is configured so as, during theproper operation of said household refrigeration appliance, to operatethe fan 22 in a closed loop speed-controlled manner according to adesired rotational speed n_(desired) that is specified at leastindirectly by the electronic control unit 9, and during an inspectionmode to operate the fan in a manner without closed loop speed control,to ascertain the actual rotational speed n_(actual) of the fan 22 and toevaluate the actual rotational speed by means of the electronic controlunit 9 in order to detect an abnormal operating state of the fan 22, inparticular to detect an icing-up of the evaporator 20.

In order to determine the actual rotational speed n_(actual) of the fan22, the household refrigeration appliance 1 comprises in the case of thepresent exemplary embodiment a tachometer 33 that measures the actualrotational speed n_(actual) of the fan 22 or rather of its fan wheel 24.The output signal of the tachometer 33 that comprises informationrelating to the actual rotational speed is supplied inter alia forevaluating purposes to the electronic control device 9.

The household refrigeration appliance 1 comprises in the case of thepresent exemplary embodiment an inverter 31 that has pulse-widthmodulation and is provided so as to control the fan 22. The inverter 31is operated in particular during the inspection mode with apredetermined duty cycle that is allocated to the inspection mode.

In the exemplary embodiment, the household refrigeration appliance 1comprises a closed loop controller 32 that is controlled by theelectronic control unit 9 and is provided so as control the inverter 31and to operate the fan 22 in a closed loop speed-controlled manner. Theelectronic control unit 9 supplies for example to the closed loopcontroller 32 information as to whether the fan 22 is to be operated inthe closed loop speed-controlled operation or for the inspection mode isto be operated in the operation without closed loop speed control andinformation relating to the desired rotational speed n_(desired) of thefan 22.

In the case of the present exemplary embodiment, the actual rotationalspeed n_(actual) is evaluated during the inspection mode by comparingthe actual rotational speed with a rotational speed of the fan 22 thatis to be expected for the evaporator 20 that has not iced-up and/or fora fan 22 that is not defective in general for a normal operating stateof the fan 22. On the basis of the evaluated actual rotational speed ofthe fan 22 during the inspection mode, it is possible to initiate aprocedure of de-icing the evaporator 20, in that for example theelectronic control unit 9 switches on a heating device so as to de-icethe evaporator after the prevailing cooling phase. The procedure ofde-icing the evaporator 20 may then be initiated for example if theactual rotational speed exceeds a specified threshold value during theinspection mode.

In accordance with an embodiment illustrated in FIG. 4, it is providedby means of the electronic control unit 9 specifying to the closed loopcontroller 32 the predetermined duty cycle DC that is allocated to theinspection mode to deactivate the closed loop speed control of the fanthat may be performed by the closed loop controller 32 so that the fan22 is controlled by the inverter 31 in a manner without closed loopspeed control during the inspection mode. The prevailing duty cycle DCof the inverter 31 is then the predetermined duty cycle that isallocated to the inspection mode. For the closed loop speed-controlledoperation of the fan 22 in the case of the present exemplary embodiment,the electronic control unit 9 supplies to the closed loop controller 32a different duty cycle to the predetermined duty cycle that is allocatedto the inspection mode, said different duty cycle comprising informationrelating to the desired rotational speed of the fan 22 during the closedloop speed-controlled operation.

Referring now to FIG. 4, in the case of this exemplary embodiment, asupply voltage V is switched on for the inverter 31 at the point in timet₀.

From the point in time t₁ to the point in time t₂, the fan 22 is startedup from standstill during a start-up phase. During this start-up phase,the fan 22 may be operated in a closed loop speed-controlled manner orin a manner without closed loop speed control.

From the point in time t₂ onwards, the electronic control unit 9supplies to the closed loop controller 32 the predetermined duty cyclethat is allocated to the inspection mode, said duty cycle being forexample 50%. Subsequently, the closed loop controller 32 or the closedloop function of the closed loop control is deactivated with the resultthat the fan 22 is operated in a manner without closed loop speedcontrol.

As long as the predetermined duty cycle that is allocated to theinspection mode is available at the closed loop controller 32, therotational speed of the fan 22 is not controlled in a closed loop mannerand after a relatively short settling time period may be compared withthe desired rotational speed that is allocated to the evaporator 20 thatis not iced-up. If the analysis of the actual rotational speed andconsequently of the fan 22 is completed at the point in time t3, theelectronic control unit 9 transmits to the closed loop controller 32 aduty cycle DC that differs from the predetermined duty cycle that isallocated to the inspection mode, as a result of which the fan 22 isoperated in a closed loop speed-controlled manner at a rotational speedthat is allocated to the selected duty cycle.

At the point in time t₄ in the case of the present exemplary embodiment,the duty cycle is set to 0% in order to slow the fan 22 down tostandstill. The supply voltage V of the inverter is switched off at thepoint in time t₅.

In accordance with an embodiment illustrated in FIG. 5, it is providedthat directly after the fan 22 has been started up from standstill, thefan 22 is operated initially for a predetermined period of time T_(v) inthe inspection mode in a manner without closed loop speed control andafter the end of the predetermined time period T_(v) said fan isoperated in a closed loop speed-controlled manner. Where appropriate, itis also possible to provide a start-up phase of the fan 22 fromstandstill directly prior to the inspection mode, the start-up phasebeing performed in a manner without closed loop speed control or in aclosed loop speed-controlled manner.

At the point in time t₀ in the case of this exemplary embodiment, thesupply voltage V for the inverter 31 is switched on.

At the point in time t₁, the start-up phase of the fan 22 commences andends at the point in time t₂. The duration of the start-up phase may befor example fixedly specified or may end upon a predetermined actualrotational speed of the fan 22 being achieved.

At the point in time t₂, the start-up phase ends and the inspection modecommences automatically for the predetermined time period T_(v) thatends at the point in time t₃. The closed loop speed control function isdeactivated during the inspection mode with the result that after asettling time period the actual rotational speed of the fan 22 iscompared with its desired rotational speed. After the specified timeperiod Tv, the analysis of the actual rotational speed n_(actual) andconsequently of the fan 22 is completed and the closed loopspeed-control function re-activated at the point in time t3.

At the point in time t₄ in the case of the present exemplary embodiment,the desired rotational speed is set to 0 in order for example to slowthe fan 22 down in a closed loop speed-controlled manner to standstill.The supply voltage V of the inverter is switched off at the point intime t₅.

The refrigeration circuit of the household refrigeration appliance 1comprises a compressor 60 that is illustrated in FIG. 6 and a condenser62, that are arranged for example in a machine space 61 that is locatedto the rear of the drawer 8.

The abnormal operating state of the fan 22 may also be a failure of thefan 22.

The fan 22 may be provided for example so as to convey air that iswarmed by the condenser 62 into the environment of the householdrefrigeration appliance 1. It is then possible to provide that on thebasis of a detected failure of this fan 22 the compressor 60 is operatedin a gentle operating mode. The compressor 60 is for example a closedloop speed-controlled compressor. A gentle operating mode, by way ofexample, is an operation of the compressor 60 at a lower rotationalspeed.

The condenser that is configured in particular as a roll or lamellacondenser may become contaminated, for example during operation. It ispossible to detect this in the case of the present exemplary embodimentby evaluating the actual rotational speed of the fan 22 during theinspection mode. In the case of a detected contamination of thecondenser, it may then be provided to operate the compressor 60 in thegentle operating mode controlled by means of the electronic control unit9.

The following is a summary list of reference numerals and thecorresponding structure used in the above description of the invention:

-   -   1 Household refrigeration appliance    -   2 Body, housing    -   3 Interior container    -   4 Coolable interior space    -   5 Refrigeration circuit    -   6 Door tray    -   7 Compartment trays    -   8 Drawer    -   9 Electronic control unit    -   10 Door leaf    -   11 Opening    -   20 Evaporator    -   21 Duct system    -   22 Fan    -   23 Motor    -   24 Fan    -   31 Inverter    -   32 Closed loop controller    -   33 Tachometer    -   60 Compressor    -   61 Machine space    -   62 Condenser    -   n_(actual) Actual rotational speed    -   n_(desired) Desired rotational speed    -   DC Duty Cycle    -   Tv Predetermined time period    -   V Supply voltage    -   t₁-t₅ Point in time

The invention claimed is:
 1. A method of operating a householdrefrigeration appliance that comprises a thermally-insulated body havingan interior container that delimits an interior space, a refrigerationcircuit for cooling the interior space, at least one fan, and aninverter operable with pulse-width modulation for controlling the fan,the method comprising the following method steps: during a regularoperation of the household refrigeration appliance, operating the fanunder closed loop speed control according to a specified desiredrotational speed of the fan; during an inspection mode, operating thefan without closed loop speed control, ascertaining an actual rotationalspeed of the fan and evaluating the actual rotational speed with anelectronic control unit of the household refrigeration appliance inorder to detect an abnormal operating state of the fan; and operatingthe inverter during the inspection mode with a predetermined duty cyclethat is allocated to the inspection mode.
 2. The method according toclaim 1, which comprises evaluating the actual rotational speed bycomparing the actual rotational speed with a rotational speed of the fanto be expected for a normal operating state of the fan.
 3. The methodaccording to claim 1, wherein the refrigeration circuit comprises acompressor and a condenser, and the fan is provided to convey air thatis warmed by the condenser into an environment of the householdrefrigeration appliance, and the abnormal operating state represents acontamination of the condenser and/or a failure of the fan, and themethod comprises: detecting a contamination of the condenser and/ordetecting a failure of the fan based on an evaluation of the actualrotational speed of the fan during the inspection mode; and based on thedetected contamination of the condenser and/or based on the failure ofthe fan, operating the compressor in a gentle operating mode.
 4. Ahousehold refrigeration appliance, comprising: a thermally-insulatedbody having an interior container that delimits a coolable interiorspace for storing foodstuffs; a refrigeration circuit for cooling thecoolable interior space; and at least one fan; and wherein the householdrefrigeration appliance is configured to carry out the method accordingto claim
 1. 5. A method of operating a household refrigeration appliancethat comprises a thermally-insulated body having an interior containerthat delimits an interior space, a refrigeration circuit for cooling theinterior space, and at least one fan, the method comprising thefollowing method steps: during a regular operation of the householdrefrigeration appliance, operating the fan under closed loop speedcontrol according to a specified desired rotational speed of the fan;during an inspection mode, operating the fan without closed loop speedcontrol, ascertaining an actual rotational speed of the fan andevaluating the actual rotational speed with an electronic control unitof the household refrigeration appliance in order to detect an abnormaloperating state of the fan; and operating the fan in the inspection modefor a predetermined period of time directly after starting up the fanfrom standstill and after an end of the predetermined time periodoperating the fan under closed loop speed control.
 6. The methodaccording to claim 5, which comprises starting up the fan fromstandstill during a start-up phase of the fan, and carrying out thestart-up phase immediately prior to the inspection mode.
 7. The methodaccording to claim 5, wherein the household refrigeration appliancecomprises an inverter operable with pulse-width modulation forcontrolling the fan, and the method further comprises operating theinverter during the inspection mode with a predetermined duty cycle thatis allocated to the inspection mode.
 8. The method according to claim 7,which comprises providing a closed loop controller to be controlled bythe electronic control unit and configured to control the inverter andto operate the fan under closed loop speed control.
 9. The methodaccording to claim 8, which comprises causing the electronic controlunit to specify to the closed loop controller the predetermined dutycycle that is allocated to the inspection mode, and deactivating theclosed loop speed control of the fan that may be performed by the closedloop controller so that the fan is controlled by the inverter withoutclosed loop speed control during the inspection mode.
 10. A method ofoperating a household refrigeration appliance that comprises athermally-insulated body having an interior container that delimits aninterior space, a refrigeration circuit for cooling the interior space,at least one fan, and a duct system in which an evaporator of therefrigeration circuit and the fan are arranged and which is connected tothe interior space, the method comprising the following method steps:during a regular operation of the household refrigeration appliance,operating the fan under closed loop speed control according to aspecified desired rotational speed of the fan; during an inspectionmode, operating the fan without closed loop speed control, ascertainingan actual rotational speed of the fan and evaluating the actualrotational speed with an electronic control unit of the householdrefrigeration appliance in order to detect an abnormal operating stateof the fan; and causing the fan to convey air that is cooled by theevaporator from the duct system into the interior space and wherein theabnormal operating state of the fan represents an icing up of theevaporator.
 11. The method according to claim 10, which comprisesevaluating the actual rotational speed by comparing the actualrotational speed with a rotational speed of the fan that is to beexpected for an evaporator that is not iced up and/or initiating aprocedure of de-icing the evaporator on the basis of the evaluatedactual rotational speed of the fan during the inspection mode.
 12. Themethod according to claim 11, which comprises initiating the de-icingprocedure if, during the inspection mode, the actual rotational speedexceeds a specified threshold value.